Bear with me, because the full answer illustrates why so many health articles are contradictory – or just plain misleading.

“Correlation doesn’t necessarily imply causation.”

Just because two things occur together doesn’t mean that one caused the other.

An action can cause another action, such as

Smoking causes lung cancer

Or it can correlate with another action, such as

Smoking is correlated with higher alcohol consumption

So smoking doesn’t cause higher alcohol consumption, but people who smoke are likely to drink more than others. In a similar way there is a strong correlation between vegetarianism and a healthier overall lifestyle.

The Seventh Day Adventist study on vegetarian longevity

Lentil and spinach dhal, a vegetarian recipe from the Health Defence Cookbook

A study frequently quoted on vegetarian longevity was conducted by the University of Loma Linda in California on 73,000 Seventh Day Adventists who eat little or no meat. It found that these vegetarians had lower cancer rates (especially breast cancer) and had longevity increases of 7.28 years in men and 4.42 years in women – compared with the general population.

So case closed?

Not quite. Because Seventh Day Adventists are also more likely to exercise, more likely to be married, do not smoke, do not drink alcohol and they live in a socially supportive community — all factors that also contribute to a longer life. It’s a good example of correlation.

Additionally, if you look at the Loma Linda study in detail, you find that pesco-vegetarians, who eat fish but not meat, had an even lower mortality rate than pure vegetarians.

Worldwide research on vegetarians

What worldwide research on vegetarians does show, however, is that vegetarians, in general:

Have lower blood pressure

Have a lower risk of ischemic heart disease

Have a lower risk of diabetes

Enjoy better moods [A Warwick University 2016 study on 12,000 Australians showed that reported happiness increased with every extra portion of fruit and vegetables up to 8 a day.]

Yet the largest ever meta-survey on mortality in vegetarians and non-vegetarians published in the American Journal of Clinical Nutrition found:

Balance!

My father had a favourite phrase:

“Moderation in all things – including virtue!”

It’s appropriate here, because it’s also clear from the research that it is excess consumption of red meat and processed and smoked meats that increases the risk of heart disease, kidney diseases, internal inflammation and certain cancers, especially stomach cancers.

It’s also clear from a huge body of evidence that fruits and vegetables have very powerful protective powers over human health – so much so that the American Cancer Society now recommends 9 portions of fruits and vegetables a day.

Health benefits from animal-derived nutrients too

But that doesn’t necessarily mean that being 100% vegetarian will automatically deliver longevity. There are health benefits from animal-derived nutrients too – the most obvious being Omega 3 fish oil. Studies show that consumption of Omega 3 – in oily fish or as a supplement – is associated with a lower risk of heart attacks, dementia, inflammatory diseases, and depression.

Additionally, a 2006 study in Mechanisms of Aging and Development suggests that a key nutrient in meat – carnosine – may help prevent glycation.

Glycation is one of the drivers of ageing, where excess glucose binds to body proteins, distorts them and inhibits their function. The outward manifestation is skin wrinkling, but the effect of glycation internally can include a loss of elasticity in the arterial systems, resulting in hypertension and atherosclerosis. Glycation is also involved in cataracts, some cancers, and Alzheimer’s disease.

Finally, evolutionary biologists are confident that it was the regular eating of meat that lead to the extraordinary expansion of human brain capacity that began some 2½ million years ago.

The Mediterranean Diet is probably the ideal

All of this, I suggest, supports the conclusion that the Mediterranean Diet, featuring mostly fruits and vegetables, with eggs, cheese, limited meat (often lamb rather than beef), fish including oily fish, and moderate red wine consumption, is not just enjoyable, but probably close to the ideal diet. See also https://nutrishield.com/blue-zones-healthy-longevity/

Of course many people are vegetarian for more than health reasons. Many of us, for example, are find the conditions of chickens in factory-style egg farms appalling and will willingly pay the extra for free range meat, chicken and eggs. And sustainability issues suggest that we need to limit our consumption of meat.

The wrong question?

But should our diet include some meat? In purely nutritional terms – probably yes. And I think that: ‘Do vegetarians live longer?’ is perhaps the wrong question.

A better question might be ‘Does a diet largely featuring fruits and vegetables enable you to live healthier for longer?’

Dr Paul Clayton

Past President of the Forum on Food and Health at theRoyal Society of Medicine.

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“Heart disease, cancer and Alzheimer’s are three killers that only appear to be age related”, says Dr Paul Clayton, who has spent over 35 years researching health and nutrition. “Yes, they strike more often as people get older, but that’s not so much due to the passing of the years as it is to the accumulation of more and more damage to DNA and body tissues.”

“Prevent or slow that damage and you hugely increase your chance of staying healthy and disease free.”

His book, Health Defence, draws lessons from world-wide research on the societies and individuals who stay fit and healthy irrespective of age. It’s a blueprint for healthy living.

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